EAB kills all ash species and is considered to be one of the most destructive tree pests ever seen in North America. The invasive beetle has been found in three Iowa locations. Allamakee County was declared infested in May 2010, Des Moines County in July 2013 and Jefferson County in August 2013.

Control Is Possible

“The best way to protect ash trees and control EAB is to treat the trees before they are infested,” said ISU Extension and Outreach entomologist Mark Shour, one of the publication’s authors. Research in the past two to three years has demonstrated that with appropriate insecticide treatment EAB can be kept from infesting healthy trees. In addition, treatment may kill EAB in trees with less than 30 percent dieback.

Insecticide products available to homeowners can be applied using a soil drench for trees up to 20 inches diameter (60 inches circumference) or as a granular application for trees up to 12 inches diameter (36 inches circumference). Both treatment methods are applied 1-2 feet from the base of the tree and need to be applied each year, Shour said.

Commercial pesticide applicators have several active ingredients available, including azadirachtin, dinotefuran, emamectin benzoate and imidacloprid, as well as several methods of product delivery — basal bark spray, soil drench, soil injection or trunk injection. One product, Tree-Age®, has demonstrated effective control of EAB for two years from one application; all other products are effective for only one season, Shour said.

“If you live within 15 miles of the known Iowa EAB infestations and you want to make a long-term commitment to caring for your ash trees, then using one of the registered products is warranted,” Shour said.

When to Treat

“Research has shown that spring is the best time of the year to treat for EAB, but fall treatments also are possible for some products having imidacloprid as the active ingredient,” Shour said. “For the current year with dry soil conditions, however, the spring of 2014 is our best option if a treatment is warranted. When there is good soil moisture, Tree-Age® can be used for healthy ash trees with a full canopy of leaves throughout the growing season.”

Read the Label

Read the product label before using any pesticide, Shour warned. Some insecticide products have annual per-acre limits for treating EAB. This means that if a property has several ash trees on it, only a few trees, based on their size, can be treated using soil application methods — drench, injection or granular — or basal bark treatment. Other trees would have to be treated using trunk injection to protect them from EAB.